Large FC loss despite SLAMming for almost a week


May 23, 2015
Amesville, ohio
Hello -

Been a rough year getting my pool open. Finally feel I’m on the right track but have been having issues with losing large amounts of chlorine every day despite slamming for almost a week and not seeing any algae in the water/in the pool (still can’t see everything though as water is still cloudy). I’m wondering if I need to up my CYA? The pool is in full sun for 10+ hours a day pretty much. CYA at last check before SLAM was 35. I’ve been holding my FC level at 16 as I rounded up to 40 for my numbers.

Just an example of what is happening - today I checked pool in the morning around 8:30. There had been about a 2ppm FC loss. Added enough to bring it back up to 16. Checked at 11:30ish…had lost down to 9. Added again to being up to 16. Checked at about 2, lost down to 8. Again I checked at about 6 and lost down to 9. Just checked the pool at 9 and lost down to 10. I would have expected that much loss in the beginning of the SLAM but this seems a large amount to still be losing.

All my other numbers were in range before I started the SLAM. We did get a large amount of rain though (2 inches) one day and that normally means my PH rises, but I haven’t tested bc of the SLAM.

Would appreciate any help/suggestions.

Thank you!

I’ve attached a picture of the pool I took this afternoon.


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Gold Supporter
Bronze Supporter
Nov 30, 2019
Pawleys Island, SC
Pool Size
Salt Water Generator
SWG Type
Hayward Aqua Rite (T-15)
Are you testing after adding liquid chlorine to make sure you’re achieving the FC 16 that you think you are? Your believed pool capacity may not be right or your liquid chlorine may be reduced in potency.
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